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vvishwaskumar • Sep 19, 2009

calculation....for bicycle

what is the torque required to run the bicycle having the weight of 100 kg. assume data self regarding:

1) friction
* rolling friction take dia of tyre= 18"
* crank radius= 6.75"
* chain and sprocket friction assume and show how it can be assume
* axle friction...
etc.

and anything you want to take into consideration regading ..please assume..

vvishwaskumar • Sep 20, 2009
where are u guys...
raj87verma88 • Sep 21, 2009
You won't get an answer to this question. We are not going to solve a homework question.
Do this yourself or atleast share what you did, so that someone can point out your mistake, if any.
vvishwaskumar • Sep 21, 2009
raj87verma88
You won't get an answer to this question. We are not going to solve a homework question.
Do this yourself or atleast share what you did, so that someone can point out your mistake, if any.
sorry, u r taking it as homework....thats ur thinking and keep it urself.....if anyone interested please reply.... i hv also received this from someone like you..ok
gohm • Sep 21, 2009
raj87verma88 • Sep 21, 2009
sorry, u r taking it as homework....thats ur thinking and keep it urself.....if anyone interested please reply.... i hv also received this from someone like you..ok
Unless and until you prove that you have tried solving it yourself, such questions will not be entertained here. Reread your question and tell me what does it look like.
4d1 • Sep 25, 2009
what is the torque required to run the bicycle having the weight of 100 kg. assume data self regarding:

1) friction
* rolling friction take dia of tyre= 18"
* crank radius= 6.75"
* chain and sprocket friction assume and show how it can be assume
* axle friction...
etc.

and anything you want to take into consideration regading ..please assume..

100 kg bicycle 😕 (laden or unladen)

anyways ..

Assuming no gears and that the weight is equally shared between the two wheels, the load to be moved at the driven wheel is 50 Kg. If the radius of the driven wheel is 460mm and that of the crank arm 170mm then their ratio is 2.7, If the chain wheel at the crank has a radius of 86mm and that of the rear sprocket wheel is 25 mm, then their ratio is 3.4, Then the effort at the pedal needed to turn the wheel is 50 x 2.7 x 3.4 = 500 kg. This is the torque required to start the bike moving. Its high because of the ratios between the wheel and crank and between chain wheels. These are not chosen to keep the torque low, but to gear up the turning speed of the wheels relative to the crank .Otherwise your legs would be going up and down like mad but the bike would move very slowly. You see this when someone is pedalling uphill in low gear. The ratios are chosen to allow a good turn of speed when the bike is moving and effort is needed only to overcome rolling friction and wind resistance.

i might be wrong..:sshhh:
vvishwaskumar • Sep 25, 2009
Rohan_sK • Sep 26, 2009
Yep, 4di is indeed correct in mentioning about the ratios between the crank and wheel radius and the sprocket radii.

Note that these radius have a major influence on the effort you put in driving the bicycle. The radii of the crank, followed by the front sprocket and then the rear sprocket should always be continously reducing so as to increase the RPM at the driving wheel ( rear ). Especially the sprocket radii must be reducing from front to rear.

This ensures that for a smaller turning of the crank there will be a relatively greater turning of the rear wheel. Thus the rider would not experience the need to do very fast pedalling to move just a short distance. The Torque required would however be T = F.d where d is the raidus of the driving wheel and F = total load.

Had the radii of the crank and sprocket been in increasing order the bicycle would be moving at very low speeds for same RPM of the crank eventually tiring the rider due to quicker pedalling required.
vvishwaskumar • Sep 27, 2009
thanx rohan.. but is there any practical method to calculate the effort applied to pedal of a bicycle....as on measuring with spring balance i got 40kg for medium loading...